A primary controlling factor with regard to the present invention is the need for miniature operative elements, for use in dental drill technology, recognizing that the dental drill not only has to be held comfortably and firmly within the hand or fingers of the dentist, but to a large extent has to be of sufficiently small size as to be placed virtually within a dental patients mouth with room to spare in order to manenuver as required during a drilling procedure. Accordingly, it is not only undersirable but unthinkable to have practically a device having numerous large elements in the making-up of the structure of a dental drill.
It is thus accordingly noted that the present invention is not the first to recognize the need for both forces parallel to the shaft axis and transverse to the shaft axis. Nor is the present invention the first to utilize the concept of magnets to achieve such forces for stabilizing the shaft against axial and transverse-plane movement. For example, U.S. Pat. No. 4,128,280 granted December 1978 to Purtschert in its FIGS. 1, 3, 4, 7 and 8 illustrated multiple magnets having opposing poles to prevent lateral movement of the shaft in a direction of a plane transverse to the axis of the shaft, and FIGS. 5 and 6 illustrate other plurality of magnets placed with opposing repelling poles to stabilize against movement of the shaft axially responsive to outside forces and while the shaft is rotated by its drive; in likewise opposing repelling facing of like-poles to prevent axial movement of the shaft, there is FIG. 4 of U.S. Pat. No. 4,153,993 to Kataoka et al. There are other even less relevant patents such as the radial bearing magnets of U.S. Pat. No. 3,958,842 to Telle, and of U.S. Pat. No. 4,072,370 to Wasson. There is the multiple magnets vertical suspension system also of Stone et al. of U.S. Pat. No. 3,493,275. In the Stone et al. patent, as is the situation in the Purtschert patent, there are separate pairs of patents to achieve the separate functions, namely one set of patents to prevent movement of the shaft in axial directions, and an additional set of magnets to prevent movement of the shaft laterally, i.e. transversly of the longitudinal axis of the shaft. Such patent typify the above-noted undesirable utilization of a plurality of elements to achieve the total bearing function, with a result of a very large machine of a size that would be totally unsuitable for miniature requirements of a dental drill of optimum small size; such problem is compounded because the magnets utilized in these patents not only require the plurality of sets of magnets, but the permanent magnets in order to exert sufficient force to stabilize properly and to a minimum required degree for a high-speed drill and high pressures to which a dental drill is subjected, must be of sizes factually much larger acknowledged or shown in the preceding noted prior art patents. That is to say, there is no way that miniature permanent magnets shown in those patents would work with sufficient power, and to use sufficiently large magnets would render the combination unthinkable too large for use in dentistry.
On the other hand, there truly has heretofore existed a great need for an improved dental drill hopefully devoid of the vibration problem and wearing ball bearings that are still utilized conventionaly in even the latent dental drills, for reason of lack of any satisfactory alternative practically workable. More particularly, the modern air turbene drills are very high speed drills with the result that the bearings have only a limited life, such being a very costly matter, as well as bothersome problem. Dentist have sufficient problems to be concerned with without having to worry about the bearings of the drill.